This invention relates to fluorine-substituted hydrocarbons, and more particularly to processes for producing CF3CHxe2x95x90CF2, CF3CClxe2x95x90CF2 and saturated derivatives thereof such as CF3CH2CF3, CF3CH2CHF2 and CF3CHFCF3, and to compositions comprising the saturated derivatives (e.g., azeotropes of said saturated derivatives with HF and uses of said azeotropes).
A number of chlorine-containing halocarbons are considered to be detrimental toward the Earth""s ozone layer. There is a world-wide effort to develop materials having lower ozone depletion potential that can serve as effective replacements. For example, the hydrofluorocarbon, 1,1,1,2-tetrafluoro-ethane (HFC-134a) is being used as a replacement for dichlorodifluoromethane (CFC-12) in refrigeration systems. The production of hydrofluorocarbons (i.e., compounds containing only carbon, hydrogen and fluorine), has been the subject of considerable interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishants and power cycle working fluids (see, e.g., PCT International Publication No. WO 93/02150).
A process is provided in accordance with this invention for producing pentafluoropropenes of the formula CF3CXxe2x95x90CF2, where X is H or Cl. The process comprises hydrodehalogenating CF3CCl2CF3 with hydrogen at an elevated temperature in the vapor phase over a catalyst comprising at least one component selected from the group consisting of elemental metals, metal oxides, metal halides and metal oxyhalides; wherein the metal of said hydrodehalogenation catalyst component is selected from copper, nickel, chromium and mixtures thereof and the halogen of said halides and said oxyhalides is selected from fluorine, chlorine and mixtures thereof.
This invention further provides a process for producing the hydrofluorocarbon CF3CHFCF3. This process comprises (a) hydrodehalogenating CF3CCl2CF3 with hydrogen as indicated above to produce a product comprising CF3CClxe2x95x90CF2, CF3CHxe2x95x90CF2, HCl and HF; and (b) reacting the CF3CClxe2x95x90CF2 produced in (a) with HF to produce CF3CHFCF3.
This invention further provides a process for producing the hydrofluorocarbon CF3CH2CHF2. This process comprises (a) hydrodehalogenating CF3CCl2CF3 with hydrogen as indicated above to produce a product comprising CF3CClxe2x95x90CF2, CF3CHxe2x95x90CF2, HCl and HF; and (b) reacting at least one of said CF3CClxe2x95x90CF2 and CF3CHxe2x95x90CF2 produced in (a) in the vapor phase with hydrogen to produce CF3CH2CHF2.
This invention further provides a process for producing CF3CH2CF3. This process comprises (a) hydrodehalogenating CF3CCl2CF3 with hydrogen as indicated above to produce a product comprising CF3CClxe2x95x90CF2, CF3CHxe2x95x90CF2, HCl and HF; and (b) reacting the CF3CHxe2x95x90CF2 produced in (a) with HF to produce CF3CH2CF3.
Azeotropic compositions (e.g., an azeotropic composition consisting essentially of from about 29.9 to about 41.3 mole percent HF and from about 70.1 to 58.7 mole percent CF3CHFCF3) are also provided which comprise CF3CHFCF3 and HF wherein said HF is present in an amount effective to form an azeotropic combination with said CF3CHFCF3.
The present invention further provides a process for recovering HF from a product mixture comprising HF and CF3CHFCF3. The process comprises (1) distilling the product mixture to remove all products which have a lower boiling point than the lowest boiling azeotrope containing HF and CF3CHFCF3; and (2) distilling said azeotrope to recover HF as an azeotropic composition containing HF and CF3CHFCF3.
This invention further provides a process for producing compositions comprising (c1) a compound selected from the group consisting of CF3CHFCF3, CF3CH2CF3 and CHF2CH2CF3 and (c2) at least one saturated compound selected from halogenated hydrocarbons and ethers having the formula:
CnH2n+2xe2x88x92axe2x88x92bClaFbOc
wherein n is an integer from 1 to 4, a is an integer from 0 to 2n+1 b is an integer from 1 to 2n+2xe2x88x92a, and c is 0 or 1, provided that when c is 1 then n is an integer from 2 to 4, and provided that component (c2) does not include the selected component (c1) compound, wherein the molar ratio of component (c2) to component (c1) is between about 1:99 and a molar ratio of HF to component (c1) in an azeotrope or azeotrope-like composition of component (c1) with HF. This process comprises (A) combining (i) said azeotrope or azeotrope-like composition with (ii) at least one fluorination precursor compound, wherein the precursor component (ii) is the fluorination precursor to component (c2); and (B) reacting a sufficient amount of the HF from the azeotrope or azeotrope-like composition (i) with precursor component (ii) to provide a composition containing components (c1) and (c2) in said ratio.
In addition, compositions are provided comprising: (c1) a compound selected from the group consisting of CF3CHFCF3, CF3CH2CF3 and CHF2CH2CF3; and (c2) at least two saturated compounds selected from halogenated hydrocarbons and ethers having the formula:
CnH2n+2xe2x88x92axe2x88x92bClaFbOc
wherein n is an integer from 1 to 4, a is an integer from 0 to 2n+1, b is an integer from 1 to 2n+2xe2x88x92a, and c is 0 or 1, provided that when c is 1 then n is an integer from 2 to 4, provided that component (c2) does not include the selected component (c1) compound and provided that c is 1 for at least one of the component (c2) compounds, wherein the molar ratio of component (c2) to component (c1) is between 1:99 and 41.3:58.7 when component (c1) is CF3CHFCF3, between 1:99 and 59:41 when component (c1) is CF3CH2CF3, and between 1:99 and 84:16 when component (c1) is CHF2CH2CF3.
This invention provides a process for producing 1,1,1,3 3-pentafluoro-propane (i.e., CF3CH2CHF2 or HFC-245fa) using 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (i.e., CF3CCl2CF3 or CFC-216aa).
The present invention includes the hydrodehalogenation of CFC-216aa in a manner which removes a single fluorine from an end carbon while removing at least one chlorine from the internal carbon to produce CF3CClxe2x95x90CF2 (CFC-1215xc) and CF3CHxe2x95x90CF2 (HCFC-1225zc). This hydrodehalogenation generally produces a product comprising CF3CClxe2x95x90CF2, CF3CHxe2x95x90CF2, HF and HCl, and involves the use of advantageously catalytic components employing copper, nickel and/or chromium. Suitable components include halides such as CuF, CuCl, CuCl2, CuClF, NiF2, NiCl2, NiClF, CrF3, CrCl3, CrCl2F and CrClF2; oxides such as CuO, NiO, and Cr2O3; and oxyhalides such as copper oxyfluoride and chromium oxyfluoride. Oxyhalides may be produced by conventional procedures such as, for example, halogenation of metal oxides.
The catalysts of this invention may contain other components, some of which are considered to improve the activity and/or longevity of the catalyst composition. Preferred catalysts include catalysts which are promoted with compounds of molybdenum, vanadium, tungsten, silver, iron, potassium, cesium, rubidium, barium or combinations thereof. Also of note are chromium-containing catalysts which further contain zinc and/or aluminum or which comprise copper chromite.
The catalyst may be supported or unsupported. Supports such as metal fluorides, alumina and titania may be advantageously used. Particularly preferred are supports of fluorides of metals of Group IIB, especially calcium. A preferred catalyst consists essentially of copper, nickel and chromium oxides (each of said oxides being preferably present in equimolar quantities) preferably promoted with potassium salt, on calcium fluoride.
An especially preferred catalyst contains proportionally about 1.0 mole CuO, about 0.2 to 1.0 mole NiO, about 1 to 1.2 moles Cr2O3 on about 1.3 to 2.7 moles CaF2, promoted with about 1 to 20 weight %, based on the total catalyst weight, of an alkali metal selected from K, Cs, and Rb (preferably K). When K is the promoter, the preferred amount is from about 2 to 15 weight % of the total catalyst.
This catalyst can be prepared by coprecipitating, from an aqueous medium, salts of copper, nickel and chromium (and optionally aluminum and zinc), with and preferably on calcium fluoride; washing, heating and drying the precipitate. An alkali metal compound (e.g., KOH, KF or K2CO3) is then deposited on the dried precipitate, followed by calcination to convert the copper, nickel and chromium to the respective oxides. Any soluble copper, nickel and chromium compound may be used, but the chlorides and nitrates are preferred, with the nitrates being especially preferred. Alternatively, promoters such as KOH, KF and K2CO3 may be added prior to co-precipitation.
Another group of catalysts which may be used for the conversion of CF3CCl2CF3 contains proportionally about 1.0 mole CuO, about 0.2 to 1.0 mole NiO, about 1 to 1.2 moles Cr2O3, about 0.4 to 1.0 mole MoO3, and about 0.8 to 4.0 mole CaF2, optionally promoted with at least one compound from the group consisting of MgF2, MnF2, and BaF2. Palladium or WO3 may also be present.
The catalyst may be granulated, pressed into pellets, or shaped into other desirable forms. The catalyst may contain additives such as binders and lubricants to help insure the physical integrity of the catalyst during granulating or scraping the catalyst into the desired form. Suitable additives include carbon and graphite. When binders and/or lubricants are added to the catalyst, they normally, comprise about 0.1 to 5 weight percent of the weight of the catalyst.
The catalyst may be activated prior to use by treatment with hydrogen, air, or oxygen at elevated temperatures. After use for a period of time in the process of this invention, the activity of the catalyst may decrease. When this occurs, the catalyst may be reactivated by treating it with hydrogen, air or oxygen, at elevated temperature in the absence of organic materials.
The molar ratio of hydrogen to CF3CCl2CF3 fed to the process typically ranges from about 1:1 to about 30:1, and is preferably at least about 3:1.
The hydrodehalogenation process of CF3CCl2CF3 is suitably conducted at a temperature in the range of from about 300xc2x0 C. to 450xc2x0 C., preferably from about 350xc2x0 C. to about 400xc2x0 C. The contact time of reactants with the catalyst bed (i.e., the volume of the catalyst bed divided by the volumetric flow rate at the temperature and pressure of the reaction) is typically from about 5 seconds to about 4 minutes:
The product from the hydrodehalogenation reaction of CF3CCl2CF3 comprises CF3CHxe2x95x90CF2, CF3CClxe2x95x90CF2, HCl and HF and typically other compounds such as unreacted CF3CCl2CF3 and partially reacted compounds such as CF3CHClCF3. These products may be separated by conventional means such as distillation and/or decantation and the components may be used individually. For example, CF3CHxe2x95x90CF2 (HFC-1225zc) may be used as a co-monomer for producing fluorine-containing polymers. Unreacted starting material (CFC-216aa) can be recycled to the hydrodehalogenation reactor.
Products from the hydrodehalogenation reaction of CF3CCl2CF3 which contain the unreacted CFC-216aa and optionally also contain the partially reacted compound CF3CHClCF3, after isolation from the unsaturated hydrodehalogenation products, can also be further reacted with hydrogen (e.g., using a conventional supported palladium hydrogenation catalyst). This hydrogenation can be used to produce CF3CH2CF3 (HFC-236fa), a useful fire extinguishant. If desired, the amount of HFC-236fa produced in this manner can be increased by decreasing the contact time of the CFC-216aa reactant in the hydrodehalogenation reactor.
CF3CClxe2x95x90CF2 (CFC-1215xc) may be reacted with HF to produce CF3CHFCF3 (HFC-227ea), which is a useful fire extinguishant. The reaction is typically conducted at an elevated temperature in either the liquid or vapor phase using a fluorination catalyst. For example, CF3CClxe2x95x90CF2 may be reacted with HF in the liquid phase at a temperature of from about 100 to 175xc2x0 C. over a pentavalent antimony catalyst (e.g., SbF5) to produce CF3CHFCF3; or CF3CClxe2x95x90CF2 may be reacted with HF in the vapor phase at a temperature of from about 300 to 400xc2x0 C. over an unsupported or supported trivalent chromium catalyst (e.g., Cr2O3 or Cr2O3/Alf3). Of note are embodiments where the HF produced from the hydrodehalogenation of CF3CCl2CF3 is used for CF3CHFCF3 production. Preferably, however, the mole ratio of HF to CF3CClxe2x95x90CF2 used for CF3CHFCF3 production is at least about 5:1.
The reaction products from the hydrofluorination may be separated by conventional techniques, such as distillation. CF3CHFCF3 may form azeotropic combinations with HF and/or HCl; and conventional decantation/distillation may be employed if further purification of CF3CHFCF3 is desired.
An azeotrope is a liquid mixture that exhibits a maximum or minimum boiling point relative to the boiling points of surrounding mixture compositions. A characteristic of minimum boiling azeotropes is that the bulk liquid composition is the same as the vapor compositions in equilibrium therewith, and distillation is ineffective as a separation technique. It has been found, for example, that CF3CHFCF3 (HFC-227ea) and HF form a minimum boiling azeotrope. This azeotrope can be produced as a co-product with HFC-227ea. As discussed further below, compositions may be formed which consist essentially of azeotropic combinations of hydrogen fluoride with HFC-227ea. These include a composition consisting essentially of from about 29.9 to 41.3 mole percent HF and from about 70.1 to 58.7 mole percent HFC-227ea (which forms an azeotrope boiling at a temperature between about xe2x88x9225xc2x0 C. and about 100xc2x0 C. at a pressure between about 77 kPa and about 3764 kPa). The hydrofluorocarbons (e.g., HFC-227ea) can be separated from the HF in such azeotropes by conventional means such as neutralization and decantation. However, azeotropic compositions of hydrofluorocarbons and HF (e.g., an azeotrope recovered by distillation of fluorination reactor effluent) are useful as recycle to the fluorination reactor, where the recycled HF can function as a reactant and the recycled hydroluorocarbon can function to moderate the temperature effect of the heat of reaction. Thus, for example, the process of this invention for producing CF3CHFCF3 can further comprise the steps of recovering a portion of the CF3CHFCF3 as an azeotropic composition of CF3CHFCF3 and HF and recycling said azeotropic composition to the reactor.
CF3CHxe2x95x90CF2 (CFC-1225zc) may be reacted with HF to produce CF3CH2CF3 (HFC-236fa), which is a useful fire extinguishant. The reaction is typically done in either the liquid or vapor phase with or without using a fluorinating catalyst. For example, CF3CHxe2x95x90CF2 may be reacted with HF in the liquid phase at a temperature of from about 20xc2x0 C. to about 175xc2x0 C. in the absence of a catalyst to produce CF3CH2CF3; or CF3CHxe2x95x90CF2 may be reacted with HF in the liquid phase at a temperature of from about 0xc2x0 C. to about 175xc2x0 C. over a polyvalent metal halide catalyst (e.g., SbF5, AlF3, MoF5, TaF5, NbF5, SnCl4, SbCl5 or TiCl4) to produce CF3CH2CF3. Also, CF3CHxe2x95x90CF2 may be reacted with HF in the vapor phase at a temperature of from about 150xc2x0 C. to about 400xc2x0 C. in the absence of a catalyst to produce CF3CH2CF3; or CF3CHxe2x95x90CF2 may be reacted with HF in the vapor phase at a temperature of from about 50xc2x0 C. to about 400xc2x0 C. over an unsupported or supported trivalent chromium catalyst (e.g., Cr2O3 or Cr2O3/AlF3) or other vapor phase fluorination catalysts such as AlF3, carbon or a transition metal (e.g., Co, Mn, and/or Cr) supported on AlF3. Of note are embodiments where the HF produced from the hydrodehalogenation of CF3CCl2CF3 is used for CF3CH2CF3 production. Preferably, however, the mole ratio of HF to CF3CHxe2x95x90CF2 used for CF3CH2CF3 production is at least about 1:1. Reference is made to U.S. Pat. No. 5,563,304 for a discussion of vapor phase hydrofluorination.
The reaction products from the hydrofluorination may be separated by conventional techniques, such as distillation. CF3CH2CF3 forms an azeotrope with HF (see U.S. Pat. No. 5,563,304) and may also form all azeotrope with HCl; and conventional decantation/distillation may be employed if further purification of CF3CH2CF3 is desired. The azeotropic compositions of CF3CH2CF3 include a composition consisting essentially of from about 59 to 37 mole percent HF and from about 41 to 63 mole percent CF3CH2CF3 (which forms an azetrope having a boiling point from about xe2x88x9225xc2x0 C. at 44 kPa to about 100xc2x0 C. at 2900 kPa).
In another embodiment, the HFC-1225zc and/or CFC-1215xc produced by the hydrodehalogenation reaction of this invention may be reacted with hydrogen in the vapor phase to produce CF3CH2CHF2. The reaction of CF3CClxe2x95x90CF2 and/or CF3CHxe2x95x90CF2 with hydrogen can employ a hydrogenation catalyst. Suitable hydrogenation catalysts include those which contain a metal (e.g., a Group VIII metal or rhenium). The metal may be supported (e.g., Pd supported on alumina, aluminum fluoride, or carbon) or may be unsupported (e.g., Raney nickel). Carbon-supported metal catalysts are preferred, with Pd/C being particularly preferred. The carbon support is preferably washed with acid prior to depositing the metal on it. Procedures for preparing a catalyst of Group VIII metal or rhenium on an acid-washed carbon support are disclosed in U.S. Pat. No. 5,136,113, the entire contents of which are hereby, incorporated by reference.
Of note is a process where CF3CClxe2x95x90CF2 and/or CF3Clxe2x95x90CF2 is contacted with hydrogen in the presence of a hydrogenation catalyst and in the presence of HCl and HF. The CF3CHxe2x95x90CF2 and/or CF3CClxe2x95x90CF2 may be isolated from the hydrodehalogenation reaction effluent by distillation if desired, and then passed to the hydrogenation step, with HCl and HF beings separately added in the hydrogenation step. However, it is preferred to pass the HCl and HF from the hydrodehalogenation, and more preferably the entire effluent from the hydrodehalogenation of CF3CCl2CF3 (including the CF3CClxe2x95x90CF2, CF3CHxe2x95x90CF2, HCl and HF), with hydrogen over the hydrogenation catalyst. While the hydrogenation reaction proceeds even in the absence of HCl and HF, the HCl and HF present during the hydrogenation step moderates the hydrogenation reaction. In any case, in accordance with this invention, CF3CH2CHF2 may be produced from CF3CCl2CF3 without separation and removal of HCl and HF prior to CF3CH2CHF2 production. In addition, passing the entire effluent from the hydrodehalogenation step on to the hydrogenation step avoids handling concerns associated with olefinic halogenated compounds as well as HCl and HF. The HCl and HF of the hydrogenation effluent is available for use along with other compounds thereof. For example, the HF is available for azeotropic combination with the fluorinated hydrocarbon compounds of the effluent from the hydrogenation reaction.
The contact of said hydrodehalogenation effluent with hydrogen in the presence of a hydrogenation catalyst and HCl and HF is suitably conducted at a temperature in the range of from about 50xc2x0 C. to about 300xc2x0 C., and preferably from about 50xc2x0 C. to about 200xc2x0 C. Contact time is typically from about 5 to 100 seconds, preferably about 10 to 30 seconds.
The molar ratio of hydrogen to CF3CHxe2x95x90CF2 in the hydrodehalogenation effluent typically is in the range from about 1:1 to about 50:1, and is preferably from about 1.5:1 to about 25:1, and more preferably from about 2:1 to about 10:1. Normally, at least about 100 ppm each of HCl and HF is present; and typically for each mole of CF3CHxe2x95x90CF2, the hydrodehalogenation effluent also contains two moles of HCl and one mole of HF, especially when the entire effluent from the hydrodehalogenation step is passed to the hydrogenation step.
Hydrogen can be fed to the hydrodehalogenation and/or the hydrogenation steps either in the pure state or diluted with inert gas (e.g., nitrogren, helium or argon).
Alternatively, CF3CH2CHF2 may be produced by reacting the CF3CHxe2x95x90CF2 and/or CF3CClxe2x95x90CF2 hydrodehalogenation reaction product with hydrogen in an empty reaction vessel of nickel, iron or their alloys in accordance with the disclosure of U.S. Pat. No. 5,364,992, which is incorporated herein in its entirety by reference.
The reaction products from the hydrogenation may be separated by conventional techniques, such as distillation. CF3CH2CHF2 forms an azeotrope with HF (see PCT International Publication No. WO97/05089) and may also form an azeotrope with HCl; and conventional decantation/distillation may be employed if further purification of CF3CH2CHF2 is desired. The azeotropic compositions of CF3CH2CHF2 include a composition consisting essentially of from about 84 to 44 mole percent HF and from about 16 to 56 mole percent CF3CH2CHF2 (which forms an azeotrope having a boiling point from about xe2x88x9250xc2x0 C. at 5.5 kPa to about 130xc2x0 C. at 3853 kPa).
Pressure is not critical for the hydrofluorination, hydrogenation, and hydrodehalogenation processes described above. Atmospheric and superatmospheric pressures (e.g., pressure from about 100 kPa to 7000 kPa) are the most convenient and are therefore preferred.
The hydrofluorination, hydrogenation and hydrodehalogenation reactions may be conducted in any suitable reactor. The reaction vessel should be constructed from materials which are resistant to the corrosive effects of hydrogen fluoride such as Inconel(trademark) nickel alloy and Hastelloy(trademark) nickel alloy.
The CF3CCl2CF3 used as a reactant in this process may be produced by known art methods such as disclosed in U.S. Pat. No. 5,057,634.
CF3CH2CHF2 has numerous uses including applications in compositions used as refrigerants, blowing agents, propellants, cleaning agents, and heat transfer agents.
As noted above, the present invention provides a composition which consists essentially of hydrogen fluoride and an effective amount of CF3CHFCF3 to form an azeotropic composition with hydrogen fluoride. By effective amount is meant an amount which, when combined with HF, results in the formation of an azeotrope or azeotrope-like mixture. As recognized in the art, an azeotrope or an azeotrope-like composition is an admixture of two or more different components which, when in liquid form under given pressure, will boil at a substantially constant temperature, which temperature may be higher or lower than the boiling temperatures of the components, and which will provide a vapor composition essentially identical to the liquid composition undergoing boiling.
For the purpose of this discussion, azeotrope-like compositions means a composition that behaves like an azeotrope (i.e., has constant-boiling characteristics or a tendency not to fractionate upon boiling or evaporation). Thus, the composition of the vapor formed during boiling or evaporation is the same as or substantially the same as the original liquid composition. Hence, during boiling or evaporation, the liquid composition, if it changes at all, changes only to a minimal or negligible extent. This is to be contrasted with non-azeotrope-like compositions in which during boiling or evaporation, the liquid composition changes to a substantial degree.
Accordingly, the essential features of an azeotrope or an azeotrope-like composition are that at a given pressure, the boiling point of the liquid composition is fixed and that the composition of the vapor above the boiling composition is essentially that of the boiling liquid composition (i.e., no fractionation of the components of the liquid composition takes place). It is also recognized in the art that both the boiling point and the weight percentages of each component of the azeotropic composition may change when the azeotrope or azeotrope-like liquid composition is subjected to boiling at different pressures. Thus, an azeotrope or an azeotrope-like composition may be defined in terms of the unique relationship that exists among components or in terms of the compositional ranges of the components or in terms of exact weight percentages of each component of the composition characterized by a fixed boiling point at aspecified pressure. It is also recognized in the art that various azeotropic compositions (including their boiling points at particular pressures) may be calculated (see, e.g., W. Schotte Ind. Eng. Chem. Process Des. Dev. (1980) 19, 432-439). Experimental identification of azeotropic compositions involving the same components may be used to confirm the accuracy of such calculations and/or to modify the calculations at the same or other temperatures and pressures.
It has been found that azeotropes of HFC-227ea and HF are formed at a variety of temperatures and pressures. Between 78 kPa (at a temperature of xe2x88x9225xc2x0 C.) and 3764 kPa (at a temperature of 100xc2x0 C.) azeotropic compositions consisting essentially of HFC-227ea and HF range from about 29.9 mole percent HF (and 70.1 mole percent HFC-227ea) to about 41.3 mole percent HF (and 58.7 mole percent HFC-227ea). An azeotrope of HF and CF3CHFCF3 has been found at xe2x88x9210xc2x0 C. and 21.9 psia (151 kPa) consisting essentially of about 40.9 mole percent HF and about 59.1 mole percent HFC-227ea). An azeotrope of HF and CF3CHFCF3 has also been found at 70xc2x0 C. and 261.2 psia (1800 kPa) consisting essentially of about 37.0 mole percent HF and about 63.0 mole percent HFC-227ea. Based upon the above findings, it has been calculated that an azeotropic composition of about 41.3 mole percent HF and 58.7 mole percent HFC-227ea can be formed at xe2x88x9225xc2x0 C. and 78 kPa and an azeotropic composition of about 29.9 mole percent HF and 70.1 mole percent HFC-227ea can be formed at 125xc2x0 C. and 3764 kPa. Accordingly, the present invention provides an azeotrope or azeotrope-like composition consisting essentially of from about 29.9 to about 41.3 mole percent HF and from about 70.1 to 58.7 mole percent HFC-227ea, said composition having a boiling point from about xe2x88x9225xc2x0 C. to 78 kPa to about 100xc2x0 C. at 3764 kPa.
Processes may employ azeotropic distillation of HF with a compound selected from the group consisting of CF3CHFCF3, CF3CH2CF3 and CHF2CH2CF2. Product mixtures obtained from a variety of sources can be distilled. These sources include product mixtures produced by fluorination with HF of CF3CFxe2x95x90CF2 to afford HFC-227ea/HF, fluorination with HF of CCl3CH2CCl3 to afford HFC-236fa/HF and fluorination with HF of CHCl2CH2CCl3 to afford HFC-245fa/HF. The described catalytic fluorination with HF reactions can be done in either the liquid or vapor phase using procedures known in the art. The product mixture may be distilled to remove all products which have a lower boiling point than the lowest boiling azeotrope containing HF and a compound selected from the group consisting of HFC-227ea, HFC-236fa and HFC-245fa. Such low-boiling, materials can include, for example, HCl. For continuous processes, distillate and azeotropes with higher boiling points can be advantageously removed from appropriate sections of the distillation column. The lowest boiling azeotrope containing HF and one of the following compounds, CF3CHFCF3, CF3CH2CF3 or CHF2CH2CF3 may then be distilled such that HF is recovered as an azeotropic composition containing HF together with one of the following compounds, CF3CHFCF3, CF3CH2CF3 or CHF2CH2CF3.
Where the mixture (after distilling components boiling at lower temperatures than the lowest boiling azeotrope of HF with CF3CHFCF3) consists essentially of HF and CF3CHFCF3, HF may be recovered as an azeotrope consisting essentially of CF3CHFCF3 and HF. If excess amounts of CF3CHFCF3 or HF remain after azeotropes are recovered from these mixtures, such excess may be recovered as a relatively pure compound. The distillation of azeotropes containing HF and CF3CHFCF3 may be done at a wide variety of temperatures and pressures. Typically the temperature is between about xe2x88x9225xc2x0 C. and about 125xc2x0 C. and the pressure is between 78 kPa and 3764 kPa. The process of this invention includes embodiments where azeotropic compositions containing from about 58.7 to about 70.1 mole percent CF3CHFCF3 are recovered. HF may be recovered for example, from a product mixture including CF3CHFCF3 formed by the reaction of CF3CFxe2x95x90CF2 with HF.
Where the mixture (after distilling components boiling at lower temperatures than the lowest boiling azeotrope of HF with CF3CH2CF3) consists essentially of HF and CF3CH2CF3, HF may be recovered as an azeotrope consisting essentially of CF3CH2CF3 and HF. If excess amounts of CF3CH2CF3 or HF remain after azeotropes are recovered from these mixtures, such excess may be recovered as a relatively pure compound. The distillation of azeotropes containing HF and CF3CH2CF3 may be done at a wide variety of temperatures and pressures. Typically the temperature is between about xe2x88x9225xc2x0 C. and about 100xc2x0 C. and the pressure is between 44 kPa and 2900 kPa. The process of this invention includes embodiments where azeotropic compositions containing from about 31 to about 63 mole percent CF3CH2CF3 are recovered. HF may be recovered for example, from a product mixture including CF3CH2CF3 formed by the reaction of CCl3CH2CCl3 with HF.
Where the mixture (after distilling components boiling at lower temperatures than the lowest boiling azeotrope of HF with CHF2CH2CF3) consists essentially of HF and CHF2CH2CF3, HF may be recovered as an azeotrope consisting essentially of CHF2CH2CF3 and HF. If excess amounts of CHF2CH2CF3 or HF remain after azeotropes are recovered from these mixtures, such excess may be recovered as a relatively pure compound. The distillation of azeotropes containing HF and CHF2CH2CF3 may be done at a wide variety of temperatures and pressures. Typically the temperature is between about xe2x88x9250xc2x0 C. and about 130xc2x0 C. and the pressure is between 5.5 kPa and 3850 kPa. The process of this invention includes embodiments where azeotropic compositions containing from about 16 to about 56 mole percent CHF2CH2CF3 are recovered. HF may be recovered for example, from a product mixture including CHF2CH2CF3 formed by the reaction of CHCl2CH2CCl3 with HF.
The HFC-227ea/HF azeotrope, as well as the HFC-236fa/HF and HFC-245fa/HF azeotropes can be used as an HF source to fluorinate numerous compounds. Optionally, such fluorinations can employ a fluorination catalyst. The fluorinations can be done in the liquid phase using typical catalysts such as SbCl5. The fluorinations can also be done in the vapor phase using typical catalysts such as Cr2O3. The following compounds, either individually or in mixed blends, can be fluorinated with the HF azeotrope to provide a variety of compositions wherein the ratio of the fluorination product(s) to a compound selected from the group consisting of CF3CHFCF3, CF3CH2CF3 and CHF2CH2CF3 is about 1:99, or more (depending upon the azeotropic combination of CF3CHFCF3, CF3CH2CF3 or CHF2CH2CF3 and HF used, and the degree of fluorination).
By fluorination precursors to the component (c2) compound(s) is meant compounds which react with HF (optionally in the presence of a fluorination catalyst) to produce the corresponding component (c2) compound(s). Fluorination precursors include saturated compounds having the formula
CnH2n+2xe2x88x92axe2x88x92bCla+xFbxe2x88x92xOc
wherein x is an integer from 1 to b. Examples of saturated precursors and corresponding products are as follows:
Fluorination precursors also include unsaturated compounds having the formula
CnH2n+1xe2x88x92axe2x88x92bCla+yFbxe2x88x92yxe2x88x921Oc
wherein y is an integer from 0 to b-1. Examples of unsaturated precursors and corresponding products are as follows:
Of particular note are processes where for component (b) a is 0 and b is 2n+1, or less.
These fluorinations include processes for producing compositions wherein the molar ratio of component (c2) to CF3CHFCF3 is between about 1:99 and about 41.3:58.7; the molar ratio of component (c2) to CF3CH2CF3 is between about 1:99 and about 59:41; and the molar ratio of component (c2) to CHF2CH2CF3 is between about 1:99 and about m84:16. This process comprises (A) combining (i) an azeotrope or azeotrope-like composition consisting essentially of CF3CHFCF3, CF3CH2CF3 of CHF2CH2CF3 and HF wherein the ratio of HF, to the (c1) component is at least equal to the desired ratio of component (c2) to the respective component (c1) compound with the precursor component (ii).
Of note are embodiments of this fluorination where the CF3CHFCF3/HF, CF3CH2CF3/HF or CHF2CH2CF3/HF azeotropes combined with the precursor(s) is obtained by (1) distilling a product mixture comprising HF and a compound selected from the group consisting of CF3CHFCF3, CF3CH2CF3 and CHF2CH2CF3 to remove all products which have a lower boiling point than the lowest boiling azeotropic contains HF and said compound; and (2) distilling said azeotrope to recover HF as an azeotropic composition containing HF and said compound. Also of note are processes where the fluorination precursors include precursors for at least two saturated compounds of the formula CnH2n+2xe2x88x92axe2x88x92bClaFbOc, where c is 1 for at least one of said saturated compounds.
The fluorination product components containing component (c1) and component (c2) may be separated by conventional means such as distillation, selective sorption and/or decantation. The compositions of this invention comprising components (c1) and (c2) (including at least one ether) are useful, for example, as aerosol propellants, fire extinguishants, and/or refrigerants. Some of the compounds of the component (c1)/component (c2) combinations may form HCl azeotropes. The HCl can be separated from those combinations by extractive distillation or sorption on activated carbon. A number of the combinations may boil too close together to separate by distillation, forming azeotropic blends (i.e., blends boiling within a limited temperature range). Some of the combinations may form binary or even ternary azeotropes. The azeotropes, zeotropes and individual compounds can be collected from different parts of a distillation column.
Without further elaboration, it is believed that one skilled in the art can, using the description herein, utilize the present invention to its fullest extent. The following specific embodiments are to be construed as illustrative, and not as constraining the remainder of the disclosure in any way whatsoever.